const declaration

2 files changed, 21 insertions, 3 deletions

diff --git a/baby.golem b/baby.golem
index b936f53..5e9fa57 100644
--- a/baby.golem
+++ b/baby.golem
@@ -1,6 +1,8 @@
 // simple comment
 var stack;
 var heap = 0;
+const dwidth = 396;
+const dheight = 224;
 
 // prototypes
 fn hello();
diff --git a/parse.c b/parse.c
index 922ce4d..d2e1bcd 100644
--- a/parse.c
+++ b/parse.c
@@ -31,6 +31,8 @@ int parse(const Token *tok)
 	return 0;
 }
 
+/* write unexpected token error to stderr before returning NULL,
+ * `n` is used to mark the error in code */
 static void *unexpected(const Token *tok, int n)
 {
 	fprintf(stderr, "[%d] unexpected %s %s%s%sat %u:%u\n",
@@ -42,6 +44,7 @@ static void *unexpected(const Token *tok, int n)
 	return NULL;
 }
 
+/* any chain of instructions that results in a value */
 static const Token *expression(const Token *tok)
 {
 	if (tok->type == TOK_INTEGER)
@@ -77,6 +80,7 @@ static const Token *keyword_fn(const Token *tok)
 	return tok + 1;
 }
 
+/* mutable variable declaration */
 static const Token *keyword_var(const Token *tok)
 {
 	tok += 1;
@@ -90,9 +94,7 @@ static const Token *keyword_var(const Token *tok)
 		return tok + 1;
 	if (tok->type != TOK_ASSIGN)
 		return unexpected(tok, 11);
-	tok += 1;
-	/* expression */
-	tok = expression(tok);
+	tok = expression(tok + 1);
 	if (tok == NULL)
 		return NULL;
 	if (tok->type != TOK_SEMICOLON)
@@ -100,7 +102,21 @@ static const Token *keyword_var(const Token *tok)
 	return tok + 1;
 }
 
+/* constant variable declaration */
 static const Token *keyword_const(const Token *tok)
 {
+	tok += 1;
+	if (tok->type != TOK_WORD)
+		return unexpected(tok, 10);
+	const Token *name = tok;
+	(void)name;
+	tok += 1;
+	if (tok->type != TOK_ASSIGN)
+		return unexpected(tok, 11);
+	tok = expression(tok + 1);
+	if (tok == NULL)
+		return NULL;
+	if (tok->type != TOK_SEMICOLON)
+		return unexpected(tok, 12);
 	return tok + 1;
 }